01-03 Intro to FEK

Question 1

Intracellular vs. Extracellular Enviro
—% TBW
—subdivided?
—[electrolytes]

Answer 1

INTRA
—2/3 TBW
—not subdivided
—high [K+] (~150mEq) and low [Na+] (~10mEq) maintained by Na+/K+-ATPase

EXTRA
—1/3 TWB
—subdivided: 1/4 intravasc, 3/4 interstitial
—low [K+] (~4mEq) and high [Na+] (~140mEq)

Question 2

Average fluid osmolality in body

Answer 2

~285-295mOsm/kg

Question 3

If you give 1200cc free water, how will it distribute?

Answer 3

800cc into cells (intracelluar = 2/3)
300cc to interstitium (extracelluar-interstitial = 2/13)
only 100cc stays in vasculature! (extracellular-intravasc = 1/12)

Question 4

If you give 1200cc normal saline, how will it distribute?

Answer 4

Because of Na+, almost none into cells so:
—900 (3/4) goes to interstitial
—300 (1/4) stays in vasculature

Question 5

If you give 1200cc KCl sol’n, how will it distribute?

Answer 5

You just killed your pt.

—all to cells assuming isotonic (300mOsm/kg)

Question 6

If you give 1200cc half-normal (0.45%) saline, how will it distribute?

Answer 6

Half as much stays in vasculature:
—200cc (1/6) stays in vasculature
—1000 (5/6) to interstitium/cells
like giving 600cc NS and 600cc free H2O: do it out

Question 7

creatinine handling by (healthy) kidney

Answer 7

—~90% freely filtered; ~10% secreted

—NOT reabsorbed, thus analogue for GFR

Question 8

normal GFR

Answer 8

women: 130-145L/d
men: 165-180L/d

Question 9

endocrine fxns of kidney

Answer 9

• epo
• renin, A-II, prostaglandins
• calcitriol synth

Question 10

PT

Answer 10

—50-90% of filtered substances absorbed here
—uptake usu. coupled to Na+ via COTRANSPORTERS
——1/2 to 2/3 Na+
——90% HCO3-
——~all glucose/a.a.’s
—urine leaves isotonic

Question 11

LoH

Answer 11

—Na+/K+/2Cl- pump (loop diuretics block)
—descending limb: H2O perm
—ascending limb: H2O IMperm
—countercurrent mech:
1. filtrate comes in with higher [Na+]
2. descends losing water (but not Na+!) to hypertonic medulla concentrating the urine
3. ascends losing Na+ (but not water!) into increasingly hypotonic medulla
4. leaves with more dilute urine
5. final urine [H2O] determined in CT

Question 12

DT

Answer 12

—Na+/Cl- co-transporter (blocked by thiazides)
—major site of Ca2+ reabsorption
—

Question 13

CD

Answer 13

—site of ADH & ANP action (opposite effects on Na+ channel)
—major K+ reg site
—Cl- via tight jct in between cells b/c of lumen q- caused by Na+ pumping out of lumen
—principal cells: resorb Na+ & H2O/secrete K+ aldosterone-dependent (site of spironolactone action)
—intercalated cells: maintain acid/base balance

Question 14

effect of thiazides of serum [Ca2+]

Answer 14

they cause hypercalcemia [see image]

Question 15

What hormones does the kidney produce?

Answer 15

—renin
—epo
—calcitriol

Question 16

Which hormones act on the kidney?

Answer 16

—A-II
—alodsterone
—ANP
—ADH
—PTH
—calcitriol

(epi?)

Question 17

True or False: Na+ reabsorption is stimulated by hyponatremia?

Answer 17

FALSE
—Na+ reuptake is stiumulated by the R-A-A-S system which is activated by: 1) low tubular flow and 2) low pressure at baroreceptors

Question 18

Major regulator of [K+]

Answer 18

aldosterone

—stimulates Na+ reabsorption and K+ secretion

Question 19

Effect of tubular flow on K?

Answer 19

high tubular flow (as with polyuria) —> creates gradiant favorable for K+ secretion

Question 20

Major regulators of [H+]

Answer 20

pH sensors cause release of:
—Aldosterone: stimulates H+ secretion (?)
—A-II: stimulates bicarb reabsorption (alkalosis)
[H+] also varies w/ ∆ing K+

Question 21

Main sites and actors of water regulation in kidney

Answer 21

Hypothal osmoreceptors sense ↑ osmolality (i.e. not volume) → ADH release
—low [Na+] doesn’t ↑ Na+ reabsorption but it DOES increase H2O wasting
***This is overridden in cases of significant hypovolemia where ADH takes on its “vasopressin” role and hangs onto water even in the face of hyponatremia
—ADH is regulating hormone
—H2O reabsorbed in the descending LoH
—H2O excreted in distal tubule which is water-impermeable but reabsorbs NaCl

Question 22

Body adjusts ______ to ∆ osmolality

Body adjusts ______ to ∆ volume

Answer 22

Body adjusts amount of WATER to ∆ osmolality

Body adjusts amount of SODIUM to ∆ volume

Question 23

Pt goes into renal failure s/p ACEI Rx. What do they have?

Answer 23

classically, R.A.S.
—in R.A.S., glomeruli receive so little RBF they clamp down their EAs to maintain filtration pressure
—ACEI caused dilation of the efferent arteriole causing plummeting GFR

Question 24

Triad for nephrotic syndrome

Answer 24

Proteinuria
edema
hypoalbuminemia
—qqf: hyperlipidemai
—qqf: lipiduria
usually non-inflamm

Question 25

Glomerulonephritis

Answer 25

hematuria!
—often renal schistocytes b/c RBCs damaged going through GBM
—RBC casts = nephritic syndrome

proteinuria often present, too, but less than w/ nephrotic syndrome